The invention relates generally to fabrication techniques and, more particularly, composite fabrication techniques and associated polymer composite-based products.
Structural composite products, such as wind turbine blades and aircraft structures, are composed of multiple layers. The conventional approach for curing these multiple layers involves curing all of the layers together at the same time in an autoclave or oven. In other words, the process involves applying the layers one over the other, and then subsequently curing all of the layers. The adhesion between layers is generally good but other disadvantages sometimes make this approach not practical. For instance, in manufacturing the root section of a wind turbine blades, sagging and dimensional distortion and fiber wrinkling during compaction may occur during curing cycle. Also, excessive reaction exotherm from thick parts may cause problems. Another approach for curing these multiple layers involves sequentially applying and completely curing layers one after another using a single curing mechanism. In other words, a first composite layer is cured completely before laying down a second composite layer. The second composite layer is then cured completely before laying down a third composite layer. The process adds additional composite layers in the same sequential manner using the single curing mechanism. Unfortunately, this fabrication technique creates relatively weak secondary adhesive bonds between the composite layers. These secondary adhesive bonds result in undesirably low interlaminar strength.
Hence, an improved technique needs to be developed to address the aforementioned issues.